Not applicable.
Not applicable.
The present invention relates to an apparatus for stacking articles and in particular to a stacking apparatus for flat mail pieces which stand on their edges. A stacking base is provided, upon which mail pieces are fed. A supporting wall is also provided for braking the incoming mail pieces. The apparatus includes a guiding means for controlling the fed mail pieces. Furthermore, the apparatus includes a support pallet which is linearly displaceable in a direction of the stack. The displacement may be facilitated by a scroll spring wound up on a spool so as to impart a substantially equally displaced force on the pallet in the direction of the stack. The scull spring imparts a resistance force upon the pallet. In coming mail pieces carry with them a certain kinetic energy accumulated from their motion resulting from the stacking process. This kinetic energy is imparted on the pallet as the mail piece comes into contact with it enroute to being stacked. The scroll spring counters this imparted energy. Mail pieces with a relatively high kinetic energy (v=m/s, m greater than 30 g) impact the pallet causing it to momentarily lose contact with the stack. Accordingly, stack supporting force from the pallet is momentarily lost and the incoming mail piece bounces off the supporting wall rather than coming to rest as a result of the friction fit between pallet and stack.
One solution to this problem was proposed in EP 0 626 927 B1, wherein at the pallet, additionally to the force produced by the scroll spring in the initial area of the motion area of the pallet close the stack-in point, an additional force is produced by a combined effort of a spline profile plate and the pallet. If there is a relatively heavy mail piece to be stacked, then the force necessary for the safe support which also lies above the spring force is produced at the pallet by contacting the ramp areas of the spline profile plate. This force can only change discontinuously and can only be produced in the first part of the stack of mail pieces. Although the stack becomes more elastic as it becomes larger, and a bouncing away from the stack is thereby often prevented, it can happen that also at already stacked-in stacks (for example with several stacked-in, thick, and hard mail pieces), a pulsed moving away of the pallet from the mail piece occurs with growth of the stack.
A task of the present inventive apparatus is to produce a generic stacking device with a pallet which is pressed against the stack by a spring element, wherein a pulsed removal of the pallet from the stack is prevented over the entire stacking area, independent from the strength of the kinetic energy of the mail pieces arriving at the stack-in point, such that the increased counterforce is always produced in proportion to the imparted kinetic energy.
The damping of the motion of the pallet over the entire motion area by the momentary reduction of the excessive energy of the heavier mail pieces is the more effective the higher the kinetic energy of the mail pieces to be stacked. The higher the kinetic energy of the arriving mail piece, the higher the braking moment of the damping element, caused by the higher speed, with which the pallet wants to remove itself from the stack of mail pieces.
It is advantageous to attach to the spool of the scroll spring, at a formation of the spring element as scroll spring, a rotary damper which is only effective during the unwinding motion, in such a way, that the rotating parts and the stationary parts are connected together. It is thereby advantageous to provide the rotary damper with a free-wheel.
To compensate the tolerances, it is advantageous to connect the rotary damper with the spool by a compensating coupling for deviations of position.
These and other advantages are also achieved from an apparatus for stacking articles in a stack, comprising: a base having a top surface for supporting a bottom of said stack; a supporting wall abutting said base, said supporting wall providing support for a first side of said stack, and said supporting wall comprising a guide rail running substantially parallel to said base; a pallet for supporting a second side of said stack, said pallet affixed to said guide rail; and article insertion means for inserting successive article into said stack, said articles being conveyed by said insertion means in a direction of said supporting wall and pallet such that kinetic energy from said conveyed article is imparted on said pallet; and dampening means affixed to said pallet, said dampening means providing to said pallet a counterforce in proportion to said kinetic energy.